Which port to use for vacuum advance... - Team Camaro Tech
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post #1 of 8 (permalink) Old Jul 23rd, 14, 07:59 PM Thread Starter
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Which port to use for vacuum advance...

Im working on getting my engine timed and tuned properly.
I have an older Holley double pumper 4777-2

The port that was originally used to run to the vacuum advance is up on the side of the carb, my only other port is down low in front of the carb.

WHen the engine is at idle the side port has zero vacuum on the gauge but my front port shows around 15 on the gauge.

Justin
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post #2 of 8 (permalink) Old Jul 23rd, 14, 08:35 PM
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Re: Which port to use for vacuum advance...

Quote:
Originally Posted by Leblanc View Post
Im working on getting my engine timed and tuned properly.
I have an older Holley double pumper 4777-2

The port that was originally used to run to the vacuum advance is up on the side of the carb, my only other port is down low in front of the carb.

WHen the engine is at idle the side port has zero vacuum on the gauge but my front port shows around 15 on the gauge.
The port up on the side that has no vacuum at idle is ported vacuum, used for vacuum advance from the factory on EGR equipped (pollution control vehicles which you probably don't have and most likely don't want). The port down low that has vacuum at idle is manifold vacuum and that's the one that you should run to your vacuum advance canister.

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post #3 of 8 (permalink) Old Jul 23rd, 14, 08:56 PM Thread Starter
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Re: Which port to use for vacuum advance...

Thank you! I figured that would make more sense but wanted to check. Thanks!

Justin
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post #4 of 8 (permalink) Old Jul 26th, 14, 06:36 PM
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Re: Which port to use for vacuum advance...

Use the Ported port.

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post #5 of 8 (permalink) Old Jul 26th, 14, 10:47 PM Thread Starter
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Re: Which port to use for vacuum advance...

Quote:
Originally Posted by hhott71 View Post
Use the Ported port.
Care to elaborate?

Justin
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post #6 of 8 (permalink) Old Jul 26th, 14, 11:40 PM
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Re: Which port to use for vacuum advance...

Paragraph 7.

But read whole article.

http://www.csgbenefits.org/Timing_an...dvance_101.pdf

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post #7 of 8 (permalink) Old Jul 27th, 14, 06:19 AM
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Re: Which port to use for vacuum advance...

Quote:
Originally Posted by 67RSSS View Post
Paragraph 7.

But read whole article.

http://www.csgbenefits.org/Timing_an...dvance_101.pdf
Ditto on reading this. Best article on timing I have ever read. Some people will claim their engine runs best with ported vacuum but they are in the very small minority.
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post #8 of 8 (permalink) Old Jul 27th, 14, 10:32 AM
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Re: Which port to use for vacuum advance...

Quote:
Originally Posted by hhott71 View Post
Use the Ported port.
Not a good idea - see "Timing 101".

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